I do: twitter.com/pauley
Twitter is, from their FAQ, "a community of friends and strangers from around the world sending updates about moments in their lives." People post a short message to the service, which is then sent to everyone who's signed up to receive your messages. Messages can be sent and received by SMS text, IM, the Twitter web site, or other third party programs. Some people think of it as "an IM away message without an IM account." Some people use it as a mini-blog (as your tweets -- yes, that's what they're called -- are saved on the Twitter web page, just like mine are at the link above).
Some more info from Time magazine: Why Everyone's Talking About Twitter
So, how 'bout it... do you Twitter?
-- Pauley